Good day!
I can perform the work which is required by you using one Linux box. There are some ways to do it. If your task is only about to redirect http requests to another destination, that is the simplest way with using squid proxy (squidquard) substitution of headers. The user will not guess at all that it not on that server.
But if you want to redirect all IP traffic (ftp, pop/imap, smtp etc) to destination domain(s), that will be more difficult way, probably, for 1-2 days longer. But all problems will be solved. I have a decent experience as ISP server's administrator. Many non-standard problems, similar to yours, have been solved during last 10 years. Just write me, please!